The present invention relates to an apparatus and a process for the free-forming manufacture of three-dimensional components having a predetermined shape. More particularly, the present invention relates to an apparatus and process for the free-forming manufacture of three-dimensional components, using layered discharge of a material onto a base through a programmed nozzle.
The problem of visualizing and describing solid shapes in three dimensions crosses many fields of the sciences and can create serious obstacles in the design process. Engineers of all types, and anyone faced with the necessity of visualizing conceived surfaces and associated spaces, for the purpose of communicating them to others, is benefitted by creation of three dimensional models. There exists an ongoing need to enhance the speed and accuracy of systems which aid in representing three dimensional models to those involved in the innovation cycle.
Three dimensional components have traditionally been difficult to manufacture without the use of molds. This problem has been addressed at length in the prior art. Traditionally, three dimensional forms have been described by a series of drawings made up of two dimensional projections of a body on a set of orthogonal planes passing through it. These types of representations of shapes of a complex nature are often insufficient. The hidden features are not properly illustrated, and if they are, two dimensional drawings quickly become too cluttered to read and understand.
Computer Aided Design and Manufacturing have facilitated improvements within the context of visualizing geometrically complicated shapes. However, the problem of free-forming three dimensional models has not been adequately addressed in terms of industrial efficiency to date. The prior art discloses no devices which permit the facile translation of computer designed and generated shapes to three dimensional models using a broad range of materials.
Although conventional machines exist to generate three dimensional models, their utility has been limited by the number of steps and therefore time, required to go from the initial design to final model production. Use of extruders for this purpose has additionally been constrained by an inability to control their processing direction and speed adequately.
European patent No. EP 0426 363 A2 discloses a process tailored to the individual needs of each component to be manufactured. EP 0426 363 A2 thus requires preparation time and increased costs for each application. It is first necessary to map out locations needed to apply the liquefied material to be discharged. Then generation of control data is required for these locally defined and proportioned material discharges. Finally, the material is discharged through a nozzle system.
According to EP 0426 363 A2, liquefied material is discharged in pre-determined places by a controllable nozzle head. The component is thus produced by free-forming during a series of time consuming and discrete steps. The discharge of different materials requires a nozzle which is adapted to the respectively required material properties. At least one computer is used for data processing, process control and visual display. As shown by this conventional arrangement, a thermoplastic raw material is discharged through the nozzle. Modelling takes place in layers. A bar-shaped or wire-shaped material is then fed into a process chamber. Through temperature variation, the material becomes molten. This step occurs directly prior to entry into the nozzle located at the terminal sector of the process chamber. The molten material is then discharged through the nozzle under pressure. The pressure is provided by pushing the bar-shaped or wire-shaped material through the process chamber.
Longstanding difficulties with this process include the limitation that it is often difficult to terminate the discharge process. This is because the discharge cannot be stopped immediately when the material is prepared for removal from the process chamber assembly. Likewise, the described arrangement only works for materials with a low melting point, such as plastics or waxes. Materials with high melting points do not work effectively. This is because it is impossible to reach sufficiently high temperatures within the short section of the process chamber.
Furthermore, in the known arrangement, the material in the nozzle can never be fully discharged. This is because no pressure can be applied after the bar-shaped material is used up. Thus the remaining material stays in the nozzle and in the space immediately prior to the nozzle. The only way to discharge the remaining material is by feeding in a new piece of the bar-shaped material.
An additional shortcoming of the prior art is the difficulty in manufacturing components consisting of different materials. Due to the limitations discussed above, this can only be accomplished by using several separate nozzles.